HIV Tests; What are the common Types?

There are different types of HIV Tests. Each test type is looking for a different markers for HIV. HIV antibody tests look for the presence of antibodies in the blood of the person. While antigen tests , each one of them looks for a specific HIV antigen. An RNA test looks for the genetic material of the virus.

Main Types of HIV Tests

After exposure to HIV infection, the virus cannot be detected directly during the first few days after exposure. Our body needs several days for HIV markers to appear in the blood or saliva. The genetic material of the virus is the first marker that can be detected , using the RNA test, a technique called (PCR). Using PCR test, HIV infection can be detected after 6 days from exposure in some, after 10 to 14 days to be detected in all infected persons.

Infection can also be diagnosed by another test, that is HIV antibodies test. Our body needs a longer period after infection to develop enough antibodies to be detected by the test. In some infected persons, it can be detected after two weeks, but it needs 90 days to be detected in all infected persons.

Which HIV tests should I choose?

When do you have to undergo testing? As mentioned above, HIV infection cannot be detected in the first few days after exposure. So, when exactly can you be tested? It depends on the test type available, and how many days since exposure to infection. Here are the 3 test type for HIV diagnosis, arranged according to availability and cost:

1- HIV Antibody Test

HIV Antibody Test is the most commonly used of all HIV Tests, because it is the most affordable and also available in all laboratories. To Have an accurate result with HIV Antibody Test , you need to undergo for testing after 90 days from exposure (window period of HIV Antibody test). That is why Antibody test is not recommended, while Combo test is a better option.

There are several generations, the most recent of which is the third generation. Even it is available and cheap, but takes up to 90 days to detect accurately the infection. There is a new test called 4th generation. It is a combination of Antibodies and Antigen p24 detection. $th generation test can detect the infection earlier.

2- HIV Antigen Test

This test can detect the presence of P24 ( an HIV antigen) as early as 16 days. But to get accurate result , you need to to do the test after 28 days from exposure (window period of HIV Antigen test). A commination of Antigen with Antibodies, that called COMBO Test, can give more accurate results. COMBO test now is commonly used in many countries, while Antigen test alone is rarely used.

3- RNA (PCR) Test

It is the most accurate and fastest, where the infection can be detected after few days of exposure. But it is more complicated than other test and not available except in specialized laboratories. It is also the most expensive of the 3 types. PCR test can give accurate results after 10 t0 14 days from exposure.

Summary of HIV Tests Main Types:

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Bottom line:

HIV Tests are mainly three types, one detecting the antibodies produced against HIV, another detecting the antigen (surface antigen of the virus) and the third for detecting the virus genome. Which one to choose depends on how many days from exposure to infection. If you were exposed recently then RNA test is the best for you. Otherwise you can undergo for Combo test and HIV antibody test.

Sources:
– https://app.hubspot.com/live-messages/20134706/inbox/
– https://i-base.info/guides/testing/